Magneto



May 1, 1951 H. G. cox 2,550,975

MAGNETO 1, 1951 H. G. cox 2,550,975

MAGNETO Filed Feb. 1, 1947 2 Sheets-Sheet 2 mum a I IN VEN TOR.

Patented May 1, 1951 Henry Grandison Cox, Rockford, Ill., assignor to 1.1. Case Company, Racine, Wis., a corporation of Wis'consin Application February 1, 1947, Serial. No. 725,815

6 Claims.

This invention relates to a magneto device and particularly has reference to the timing of rotary armature magnetos.

Magnetos are timed so that the spark produced within the engine cylinder will occur at a predetermined time for the combustion of the compressed fuel. In order to accomplish this order of events the contact-breaker points will be opening as the piston of the cylinder in which the fuel is to be exploded by the spark approaches top dead center preparatory to starting the combustion stroke. In engines of certain manufacture the timing of the magneto spark impulse and the engine stroke is accomplished by rotative adjustment of the magneto housin relative to the engine. The invention is directed to means for facilitating such adjustment and maintaining the same as when remounting' the magneto after servicing and the like.

The principal object of the invention is to provide a simple indexing or timing device which will correctly time the magneto with the engine cylinders to provide for proper combustion of the explosive mixture compressedin the cylinders.

Another object of the invention is to provide an indexin and timing device which correctly times the magneto where it is difficult to observe the breaker points for setting due to inaccessibility.

A further object of the invention is to provide an indexing and timing device which utilizes a drainage opening for indexing the magneto and does not necessitate the uncovering of any of the moving parts of the engine and magneto.

Another object is to provide for the easy reassembly of the magneto and engine in correct timed relation.

These and other objects of the invention will appear hereinafter in connection with the followin description of the drawing illustrating an embodiment of the invention.

Figure 1 is a side elevational view of a magneto with parts broken away and sectioned;

Fig. 2 is an end view of the magneto of Fig. 1;

Fig. 3 is a transverse section taken on line 3-3' of Fig. 1;

Fig. 4 is a perspective view of the key of the invention;

Fig. 5 is a diagrammatic view showing an engine cylinder and piston and parts of a magneto in predetermined relative positions at the time of installation of the magneto;

Fig. 6 is a detail view of the breaker arm and cam operation; and w Fig. '7 is an elevatlonal view showing a magneto assembled on an engine.

The drawings illustrating the invention show a magneto located in the generally confined space between the engine I and fire wall 2 of an airplane, with only portions of the engine and fire wall being shown.

The magneto in general comprises a frame 3 which is closed at the top by the cover 4 and at the rear by the distributor cap 5. The front of frame 3 has a flange 6 complementary to flange I on engine I for securing the magneto to the engine by suitable bolts.

The main shaft 8 of the magneto, only a portion of which is shown, extends longitudinally of frame 3 and is supported for rotation within suitable bearings in frame 3. The shaft 8 is rotated from engine I by the impulse coupling 9 at the forward end of frame 3 and which need not be further described since it forms no part of this invention.

The operation of the magneto is diagrammatically shown in Fig. 5 of the drawings. Asthere shown, a magnetic rotor or armature It] is disposed on shaft 8 to rotate therewith as shaft 8 is rotated from engine I by the impulse coupling 9, and to set up magnetic impulses in a core II for inducing a flow of current in the primary coil I2. The primary current flows from coil I2 through lead i3 to breaker bar spring I4 and thence through the movable breaker arm I5; then through the contact points to stationary contact support or arm I6 and to ground on frame 3 at H. It then travels through frame 3 to a point I8 where it is picked up and. transmitted back to coil I2 by lead I9. The condenser 20 is connected in parallel with the points of arms I5 and I6 from lead wire I3 to frame 3 to eliminate destructive sparking at the contact points when the points are opened.

The spring I4 normally biases the contact points of arms I5 and I6 together by engagement with pivoted arm I6 which is pivoted on pin 2|. However, at suitable intervals of current flow the cam 22 which is rotated by shaft 8 separates the points of arms I5 and I6 by movement of arm l5 against spring I4.

The breaker arm I5 is mounted on an insulating bushing on pin 2i, and cam 22 is either of insulating material or is mounted on an insulating sleeve on shaft 8 to avoid shorting of the breaker contacts.

When the points are open the current flow described is interrupted and a high voltage is then induced by core II in the secondary coil 23. This high voltage secondary current flows through lead 24 to a rotatable distributor arm 25 through which it"is' communicated to se ment 3 26. It then flows from segment 26 to terminal 21 and is transmitted by lead 28 from terminal 21 to the spark plug 29 on cylinder 30 of engine I.

At the time the flow of current to cylinder 33 occurs the piston 3| of the cylinder should be substantially at top dead center preparatory to starting the combustion stroke, and the fuel in the cylinder is exploded by the spark created in the cylinder by the flow of secondary current thereto as described.

Only one cylinder and piston are shown for purposes of illustration, since if the magneto points are timed to the operation of the piston of one of the cylinders it will also be properly timed with the pistons of the remaining cylinders.

At the time that the magneto is installed on engine l by bolting flanges 6 and] together, pis- 3 ton 3| is first located at the point Where it is desired to have the spark occur, which may be, for example, in advance of top dead center, and it is necessary that the magneto be indexed so that the contact points of arms l5 and it are just opening.

In order to insure that the contact points are set to open in correct timed relation to the top dead center position of piston 3!, a gauge or indexing means is employed as described hereinafter. 'i

The recess or opening 32 is provided in the bottom of the magneto frame 3 adjacent flange 6.

This recess extends upwardly around magneto shaft 3 and is normally employed for drainage purposes.

A hole 33 is drilled in shaft 3 in radial alignment with recess 32 at the line where shaft 8 is exposed through the recess. Hole 33 is made in shaft 8 at the factory after assembly of rotor iii and cam 22 on shaft 8. The point on shaft 8 at which hole 33 is drilled is determined by the position where cam 22 thereon has engaged arm iii to separate the breaker point thereof from the point of arm l6 and will establish the spark in the engine cylinder.

In order to hold shaft 8 with hole 33 in radial alignment with recess 32, the pin 34 on the upper end of the flat key 35 is inserted within the hole. Key 35 is of a shape to accurately fit in recess 32 and is confined by the walls of frame 3 against rotary movement of shaft 8. The key is normally tapered to Wedge it in place, and the opening 35 is provided in the body thereof for engagement of the key by a suitable tool to remove it from recess 32.

4 pling 9 and the magneto is correctly timed to the engine.

As shown in Fig. 6 arm [5 is slotted to make it adjustable by loosening the screws 31 which hold it in place on frame 3.

When the points become worn and are re-' placed, key 35 is inserted in recess 32 with pin 34 in hole 33 to hold shaft 3 against rotation. This locates cam 22 in engagement with breaker arm I5 to normally open the points as described. When the points are replaced they are thicker than the old worn points and. therefore open at a different time or may not open at all, and arm I5 is adiusted to take care of the greater thickness of the points by loosening screws 3'! and then securing the arm in place again by the screws at a position Where the points of arms 16 and iii are just separating when engaged by the cam 22. As the points become worn and are filed arm l6 may also be moved, from time to time,

toward arm M5 by adjustment as described until the points need to be completely replaced. Key 35 always holds shaft 3 at a position Where the cam 22 is starting to open the points so that the Serviceman can readily locate arm [5 to time the cam operation to the new or adjusted position.

In magnetos where recess 32 is not available a special opening may be provided in the frame of the magneto to receive the key described.

The assembly of the magneto on the engine is simplified by the employment of key 35. In the assembly of a magneto with an engine, key 35 if not disposed in place at the factory is first inserted in recess 32 with pin 34 in hole 33 to key shaft 8 to the magneto housing and establish the correct position of the breaker points for assembly purposes.

The magneto is then assembled on the engine by aligning the corresponding bolt holes of the Key 35 is normally located in place at the factory toprevent the magneto from getting out of adiustment by rotation of shaft 8 in shipping although it may be inserted by the operator at any time before the magneto is installed. The magneto points are not properly indexed until shaft 3 is rotated to a position where it is possible to insert pin 34 of key 35 in hole 33 and where distributor arm 25 engages the segment 26 corresponding to the particular cylinder of the engine employed for the timing operation.

The magneto, With shaft 8 held against rotation and the breaker points and distributor properly indexed by key 35 may be assembled in place on the engine without requiring observation of the breaker points during assembly.

After the magneto is installed on the engine, at which time piston 3| of cylinder 35 is approaching top dead center and the points are set to open, key 35 is removed and shaft 3 is then rotatable from engine I through impulse coucomplementary flanges 6 and 1, respectively, of the magneto and engine and securing the flanges together by suitable bolts. Key 35 maintains impulse coupling 9 on the end of shaft 8 in a predetermined position relative to the frame 3 so that the impulse coupling 9 may be coupled to the magneto drive coupling 38 of the engine by rotational adjustment of the magneto housing. The necessary adjustment between the flanges 6 and 1 may be obtained by enlarging one of the bolt holes on each of the flanges as shown in Fig. 2. The invention eliminates the necessity of rotating the magneto upon assembly to obtain the correct spark because key 35 locates the magneto housing, the shaft 8 and impulse coupling 9 in a predetermined position which is correlated to a corresponding predetermined position for the engine crankshaft and which will provide the correct spark timing by simply bolting the magneto to the engine. The invention provides a simple timing and indexing device to time the magneto parts and to index the magneto with the engine by which it is operated. The invention is particularly advantageous in that the key is readily removable after the magneto is installed and in that it makes possible the proper timing of a magneto in cramped quarters Where it is difficult to observe the position of the contact points and the cam which opens them at spaced intervals.

Various embodiments of the invention may be employed within the scope of the accompanying claims.

I claim: I l. A magneto for supplying ignition to an internal combustion engine, comprising a mag-.

neto housing adapted to be secured to the engine, a rotary shaft in said housing adapted to be coupled to a drive shaft therefor operated by said engine, breaker points for said magneto operated by said rotary shaft and adapted to operated in timed sequence with the pistons of the engine, a removable locking member adapted to engage said rotary shaft and hold the same in a predetermined fixed indexed position relative to the housing during assembly of the shaft coupling whereby the position of the breaker points may be correlated to the position of the engine pistons without requiring observation of the breaker points and adjustment of the same during assembly, and means for securing the housing to the engine and providing limited relative adjustment therebetween to facilitate assembly of the coupling with said rotary shaft and said drive shaft in predetermined correlated positions.

2. In a magneto, a timing device employed With the actuating shaft thereof, comprising a removable indexing member confined against circumferential movement in an opening in said magneto giving access to said shaft, means keying said indexing member to said shaft to hold the shaft in a predetermined position for timing the magneto parts and for timing the magneto to the engine with which it is assembled,

means providing for manual adjustment of the magneto rotationally with respect to the engine during assembly of the same and while said indexing member is keyed to said shaf l1, and means to secure the magneto to the engine in a selected rotational position relative thereto.

3. In a magneto, a timing device employed with the actuating shaft thereof, which comprises a magneto housing having means at one end for securing the same to the engine on which the magneto is installed and providing adjustment of said housing and the engine rotatively of said actuating shaft and a removable indexing member extending through an opening in the magneto housing and keyed to said shaft to hold the shaft in a predetermined rotary position for timing the magneto to said engine when the magneto is installed thereon.

4. In a magneto, a timing device employed with the actuating shaft thereof, which comprises a magneto housing having a flange at one end for securing the same toa complementary flange on the engine on which the magneto is installed and providing limited adjustment of said housing and the engine rotatively of said actuating shaft, and a removable indexing member extending through an opening provided in the bottom of the magneto housing between the flange thereon and the body of the housing and keyed to said shaft to hold the shaft in a predetermined circumferential position for timing the magneto to said engine when the magneto is installed thereon.

5. In an engine magneto, a timing device employed with the actuating shaft thereof, which comprises a magneto housing having a flange at one end for securing the same to the engine and providing limited adjustment of said housing and the engine rotatively of said actuating shaft and having an opening provided in the bottom of the magneto housing for access to said shaft, the magneto shaft having a hole disposed to be in radial alignment with said opening when the shaft is in a predetermined position for timing the magneto to said engine during installation of the magneto thereon, and an indexing member confined in said opening against circumferential movement and having a pin projecting into the hole on the shaft to hold the shaft in the predetermined position at which the magneto is timed to the engine on which it is installed, and said indexing member being removable after installation of the magneto to free said shaft for rotation.

6. In a magneto for supplying ignition to an internal combustion engine comprising a magneto housing adapted to be secured to an engine, a rotary shaft in said housing adapted to be coupled to a drive shaft therefor operated by the engine, an armature and a cam carried by said shaft in fixed indexed relation, a coil carried by said housing for said armature, and breaker points carried by said housing and operated by said cam, the combination comprising a removable locking member carried by said housing in engagement with said shaft to secure the latter against rotation relative to said housing and said cam and armature in fixed indexed relation to said breaker points and coil respectively, a coupling for said rotary drive shaft and the drive shaft therefor operated by the engine, and means for receiving and securing said housing in adjusted assembly to said engine with said rotary shaft coupled to the drive shaft therefor and with said cam and breaker points and armature and coil in indexed relation to the drive shaft of the engine.

HENRY GRANDISON COX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,031,016 Mason July 2, 1912 1,043,116 Lee Nov. 5, 1912 1,649,060 Decker NOV. 15, 1927 2,037,083 McCormick Apr. 14, 1936 2,162,338 Larsen June 13, 1939 2,308,973 Crocker Jan. 19, 1943 2,483,667 Purdy Oct. 4, 1949 

